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Old 07-27-2012, 09:28 AM   #29 (permalink)
Daox
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I've pretty much finished up the first round of testing on the first cell. Capacity wise it isn't quite up to the 20Ah spec (I don't have the 1C discharge Ah number handy), but its fairly close. I also found that with my mottcell cells that sometimes multiple cycles tended to increase the capacity almost like the cells needed to be exercised. However, this wasn't true for all the cells I tested.

Anyway, here are a few charts.


The first test was to charge/discharge at .5C (10A). My laptop went to sleep during the charge so I only have the discharge which is thankfully the more useful (to see voltage sag).







I have a few more charts from my 1C (20A) tests. The first shows the voltage over time for the discharge cycle.





This shows the volts over time for the charging cycle.




Below you'll see the Ah put into the cell over time.

With these two charging charts, I can fairly accurately estimate the state of charge (SOC) that these cells will sit at when they are connected to my alternator on the Paseo. For example, lets say my alternator puts out 14V. 14V gives us 3.5V per cell (well below the 3.65V max charge voltage, so no need for a BMS). By looking at these charts we know the cells hit 3.5V around the .9 hour mark. By looking at the capacity chart at the .9 hour mark it looks like I'll have close to 17Ah stuffed into the batteries. This is actualy quite a bit more than I thought which is nice. Though, I do have to verify my alternator output. If the alternator puts out 13.5V (3.375V/cell) we're looking at a capacity of around 10Ah. So, a little voltage variance goes a long way.









Next up is the 2C (40A) tests. You can see the voltage is starting to sag a tiny bit more, but its very reasonable. I don't have a mottcell chart handy right now, but I'm pretty sure there is more sag at 1C on my mottcell cells than there is at 2C with these cells.

Here is the voltage over time for the discharge cycle.




Here is the voltage over time for the charge cycle.




And here is the capacity over time for the charge cycle.
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